1. Field of the Invention
The invention relates to a process and device for dispersing fibrous paper material.
2. Discussion of Background
Processes for dispersing fibrous paper material are, for example, necessary for the improvement of the quality of fibrous material, which is extracted from used paper. It is known that fibrous paper material can be homogenized and thereby significantly improved through dispersion. In many cases a fibrous material is used, which exhibits a dry content between about 15% and 35% and which has been brought to a temperature which is significantly above the ambient temperature. It is prudent to undertake the calefaction, i.e., warming, if the fibrous material already has the consistency necessary for dispersion. With this thickening process, a considerable portion of the water, which was previously still present in the fibrous material, is removed before calefaction. Through this process, first, its viscosity increases significantly in the dispersion and second, less water must be calefied. The most important machines for the thickening are worm presses and sieve presses.
With a sieve press, the fibrous material suspension is fed in between a sieve and a roll or between two sieves and pressed, so that the water is discharged. As a result, a moist fibrous material web is formed. Depending upon the operational parameters, this web has a solid matter G.S.M. between about 500 g/m2 and 2000 g/m2. Pressures which deviate from this range, however, can also be advantageous. The moist web is taken from the area of the sieve or the sieves and must, thereafter, be torn into flat pieces. These pieces are easy to calefy to the desired temperature, but a relatively long calefaction period is necessary. Thus, calefaction periods of, for example, several minutes must be accepted, especially if a temperature above 90xc2x0 C. is desired. Thereafter, the hot, friable material is fed into a disperser. The entire process requires a device that is quite expensive.
With a worm press, the fibrous material suspension is pressed between a worm conveyer and a perforated jacket surrounding it, whereby the water leaves through the jacket. The resulting pressed pulp, or plug, is pressed from the worm and breaks into pieces. Only a relatively long calefaction period can bring these pieces to the desired temperature. A further pulverization can, for example, occur in a pulverizing worm or in a system with counter-rotating rotors, which is, however, very expensive.
It is therefore a task of the present invention to create a process in which it is possible to shorten the calefaction periods and at the same time to reduce the industrial construction expenses and spatial requirements.
More specifically, the present invention involves a process for dispersing a fibrous paper web of a highly consistent fibrous paper material. The process includes loosening and pulverizing a fibrous paper material into a fine, friable fibrous material, guiding the fine, friable fibrous material into a vapor chamber in which at least one of a gaseous and vaporous heating medium mixes, calefies, and disperses the fine, friable fibrous material, and dispersing the fine, friable fibrous material in a disperser zone, the disperser zone and the vapor chamber being located in one device.
Using this process it is possible to manufacture at low cost a friable material that is sufficiently fine and can be calefied at a correspondingly quick rate. Further, according to the present invention, industrial expenditure is relatively low, since the processes of pulverization, calefaction, and dispersion can be executed in a single device.
The high-consistency fibrous paper material can either be admitted directly into the mounting of a disperser as a plug or in the form of a loose, just preliminarily crushed, high- consistency material. The material is then taken up by the first pulverization step of the disperser and pulverized and fluidized, whereby the fine, friable fibrous materials arise. By supplying vapor into the zone which succeeds the first pulverization stage downstream, the material is then calefied to the necessary temperature, whereby a relatively short calefaction period is sufficient, due to the previous, intensive pulverization. The actual dispersion, that is, alteration of material characteristics, occurs in the dispersion zone, which follows downstream.
In one aspect, the present invention involves a process for dispersing a fibrous paper web of a substantially consistent fibrous paper material. The process includes loosening and pulverizing a fibrous paper material into a fine, friable fibrous material; guiding the fine, friable fibrous material into a vapor chamber in which at least one of a gaseous and vaporous heating medium mixes, calefies, and disperses the fine, friable fibrous material; and dispersing the fine, friable fibrous material in a disperser zone, the disperser zone and the vapor chamber being located in one device.
In accordance with an aspect of the invention, the loosening, pulverizing, calefying, and dispersing may occur between a stator and a rotor of a disperser, wherein the stator and rotor comprise concentric rows of teeth which extend axially into a chamber between the stator and rotor.
In accordance with another aspect of the invention, the fine, friable fibrous material has a maximum thickness of about 5 mm. The fine, friable fibrous material may have a maximum length of about 10 mm.
In accordance with yet another aspect, the fine, friable fibrous material is spun in the heating medium and is in a fluidized state at least during a predominant portion of calefaction. A mean duration of time of the fine, friable fibrous material in the vapor chamber may be between about 0.5 and 3 seconds. The heating medium may be superheated vapor which is supplied to a radially exterior area of the vapor chamber. The heating medium may be superheated vapor which is supplied to a radially interior area of the vapor chamber. Installations may be provided in the vapor chamber to retard movement of the fine, friable fibrous material in the vapor chamber.
In accordance with an aspect of the invention, radial movement of the fine, friable fibrous material in the disperser zone is throttled. In accordance with another aspect of the invention, a maximum velocity of an instrument triggering the pulverizing step is between about 10 m/s and 30 m/s.
In accordance with yet another aspect of the invention, the pulverizing involves a pulverizing element which immediately engages a material plug which has left a draining worm. The pulverizing may involve a pulverizing element which engages fibrous pulp pieces from pre-pulverization of a moist fibrous pulp web that has run off a sieve press. In accordance with an aspect of the invention, the process further comprises calefying the fibrous paper material before the pulverizing.
In another aspect, the present invention involves a device for dispersing a fibrous paper web of a substantially consistent fibrous paper material, including an inlet for fibrous paper material, a stationary stator, and at least one rotatable rotor. The stator and the at least one rotor form a pulverizing zone including a pulverizing element located near the inlet for the fibrous paper material, where the pulverizing element includes at least one of scrapers and knives for pulverizing the fibrous material into a fine, friable material, a vapor chamber forming a ring about the pulverizing zone, the vapor chamber being for calefying the fine, friable material formed by the pulverizing element, and a dispersing zone including at least one row of teeth on the stator and at least one row of teeth on the at least one rotor which can be moved relative to the at least one row of teeth of the stator.
In accordance with one aspect, the at least one row of teeth of the stator and the at least one row of teeth of the at least one rotor form a gap of up to about 3 mm. The vapor chamber may be delimited downstream by a row of stator teeth which extend to form a gap with rotor teeth of up to about 3 mm. The stator teeth may have a distance of at least 50 mm in peripheral direction. The vapor chamber being delimited downstream by a row of rotor teeth which extend to form a gap with the stator of up to about 3 mm.
In another aspect of the invention, the vapor chamber is connected to a vapor supply line via a vapor pipe. In yet another aspect of the invention, the disperser zone is closed off radially outside by a throttle, which renders a valve opening area adjustable. The throttle may comprise a throttle ring equipped with openings, wherein the throttle ring is capable of being turned to adjust the valve opening area. The throttle comprises a throttle ring, wherein the throttle ring is capable of being axially displaced to adjust the valve opening area.
In another aspect, the present invention involves a process for dispersing a fibrous paper web in one apparatus. The process includes pulverizing a fibrous paper material into a fine, friable fibrous material, mixing, calefying, and dispersing the fine, friable fibrous material in a vapor chamber by using at least one of a gaseous and vaporous heating medium, and dispersing the fine, friable fibrous material in a disperser zone.
In still another aspect, the present invention involves a device for dispersing a fibrous paper web that includes an inlet for fibrous paper material, a stator surrounding the inlet, the stator including at least one row of teeth, a rotor having at least one row of teeth which cooperates with the at least one row of teeth of the stator, the rotor including a pulverizing element adjacent to the inlet, the pulverizing element comprising at least one of scrapers and knives for pulverizing the fibrous material into a fine, friable material; and a vapor chamber formed between the rotor and stator for calefying the fine, friable material formed by the pulverizing element.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.